package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.sql.Time;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

@Component
@Slf4j
public class CacheClient {
    @Resource
    private StringRedisTemplate stringRedisTemplate;



    public void set(String key, Object value, Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit){
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        redisData.setData(value);
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough( String keyPrefix, ID id, Class<R> type, Function<ID,R> dbFallback,Long time, TimeUnit unit){
        String key= keyPrefix +id;
        //从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //存在，返回
        if(StrUtil.isNotBlank(json)){

            return JSONUtil.toBean(json, type);
        }
        //判断命中的是否为空值
        if(json!=null){
            return null;
        }

        //不存在，根据id查询数据库
        R r = dbFallback.apply(id);
        //数据库不存在，返回错误
        if(r==null){
            //将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",RedisConstants.CACHE_NULL_TTL,TimeUnit.MINUTES);
            return null;
        }

        //存在，写入redis，再返回
        this.set(key,r,time,unit);
        return r;
    }
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public <R,ID> R queryWithLogicalExpire(String keyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback,Long time, TimeUnit unit) {
        String key= keyPrefix +id;
        //从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //不存在，返回null
        if(StrUtil.isBlank(json)){

            return null;
        }
        //命中，需要判断过期时间，需要把JSON反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        JSONObject data = (JSONObject) redisData.getData();
        R r = JSONUtil.toBean(data, type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //未过期，直接返回店铺信息
        if(expireTime.isAfter(LocalDateTime.now())){
            return r;
        }
        //已过期，需要缓存重建
        //获取互斥锁
        String lockKey=RedisConstants.LOCK_SHOP_KEY+id;
        //判断是否获取锁成功
        boolean isLock = tryLock(lockKey);
        //成功，开启独立线程实现缓存重建
        if(isLock){
            CACHE_REBUILD_EXECUTOR.submit(()->{
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key,r1,time,unit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }
                finally {
                    //释放锁
                    unlock(lockKey);
                }

            });
        }
        //返回商铺信息
        return r;

    }
    /**
     *尝试获取锁
     * @param key
     * @return
     */
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", RedisConstants.LOCK_SHOP_TTL, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    /**
     * 释放锁
     * @param key
     */
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}
